An electronic seal apparatus causes an image displaying/reading apparatus to display an electronic document. The electronic seal apparatus includes (i) a storage section for storing first identification information to be used for identifying a first digit of a user of the image displaying/reading apparatus and a first seal image of the user in association with each other, (ii) a digit identifying section for determining based on the first identification information whether or not a digit indicated on a subject image that is read by the image displaying/reading apparatus while the electronic document is displayed by the image displaying/reading apparatus is the first digit, and (iii) a sealing section for sealing onto the electronic document, in a case where the digit indicated on the subject image is determined to be the first digit, a seal image associated with the first identification information. This makes it possible to develop a system in which a seal image can be electronically sealed after finger authentication is performed even if a finger authentication scanner solely dedicated for reading an image from a digit is not provided.